Cosmetic depilatory compositions comprising a continuous aqueous phase and an oil phase

ABSTRACT

The invention provides depilatory compositions comprising: (a) a continuous aqueous phase; (b) a depilatory agent; and (c) at phase comprising (i) a non-polar coil separated from the continuous aqueous phase by a bilayer phase comprising (ii) a surfactant; (iii) a polar substance; wherein the composition is substantially free from tertiary amines; processes for their preparation; and their use degrading hair keratin.

This application is a 371 of PCT/GB98/01878 file Jun. 26, 1998.

The present invention relates to depilatory compositions in the form ofan improved oil-in-water emulsion; their preparation; and their use indegrading hair keratin.

BACKGROUND OF THE INVENTION

Compositions for removing superfluous body hair are well known and areof various types. One type of composition requires initial heatingbefore being applied to the skin in a generally molten state. It is thenallowed to solidify before being removed from the skin together withunwanted hair.

Another type of depilatory composition is in the form of a cream, whichcan be applied to the skin at room temperature. The cream includes asubstance that degrades hair keratin. Such substances tend to irritatethe skin which is a problem for users with sensitive skin. Compositionswith reduced irritancy have been sought.

SUMMARY OF THE INVENTION

The present invention therefore provides a depilatory compositioncomprising:

(a) a continuous aqueous phase;

(b) a depilatory agent; and

(c) an oil phase comprising

(i) a non-polar oil separated from the continuous aqueous phase by abilayer phase comprising

(ii) a surfactant; and

(iii) a polar substance;

wherein the composition is substantially free from tertiary amines.

However, the present inventors do not wish to be bound by the definitionof the particular structure of the composition that they believe to beformed. According to the present invention, there is further provided adepilatory composition comprising from 2% to 6% w/w of depilatory agent,from 0.2% to 20% w/w of non-polar oil, from 2% to 20% w/w of surfactant,from 0.5% to 20% w/w of polar substance and from 95.3% to 34% w/w ofaqueous phase; wherein the composition is substantially free fromtertiary amines.

DETAILED DISCLOSURE

The depilatory agent is a substance capable of degrading keratin and maybe, for example, a sulphur compound such as potassium thioglycolate,dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicylcicacid, N-acetyl-L-cysteine, lipoic acid, NaHSO₃, Li₂S, Na₂S, K₂S, MgS,CaS, SrS, BaS, (NH₄)₂S, sodium dihydrolipoate 6,8-dithiooctanoate,sodium 6,8-dithiooctanoate, salts of hydrogen sulphide for example NaSHor KSH, thioglycolic acid, thioglycerol, 2-mercaptopropionic acid,3-mercaptopropionic acid, thiomailic acid, ammonium thioglycolate,glyceryl monothioglycolate, monoethanolamine thioglycolate,monoethanolamine thioglycolic acid, diammonium dithiodiglycolate,ammonium thiolactate, monoethanolamine thiolactate, thioglycolamide,homocysteine, cysteine, glutathione, dithiothreitol, dihydrolipoic acid,1,3-dithiopropanol, thioglycolamide, glycerylmonothioglycolate,thioglycolhydrazide, keratinase, hydrazine sulphate, hydrazinedisulphate, triisocyanate, guanidine thioglycolate, hair reducing pack,calcium thioglycolate and/or cysteamine. However, the composition ispreferably substantially or, more preferably, completely free fromdepilatory agents that destroy the thermodynamic equilibrium or thesurface tension of the composition; examples of such agents includealkali metal sulphides. Preferably, the composition comprises from 2.0%to 6.0% w/w of the keratin-degrading substance in order to obtain asatisfactory depilation time of about 5 minutes.

It is preferred that the non-polar oil is in the form of droplets,although it may also be in the form of sheets. When in the form ofdroplets, each droplet of the non-polar oil is preferably individuallysurrounded by one or more than one bilayer. When in the form of sheets,each sheet of the non-polar oil is preferably separated from theadjacent sheet by one or more than one bilayer. More preferably, eachbilayer, in the case where more than one is present, is itself separatedby a bilayer aqueous phase comprising at least water and depilatoryagent.

The non-polar oil preferably has a polarity index of from 20 to 46 mN/m,more preferably from 30 to 46 mN/m. The polarity index is a measure ofthe interfacial surface tension between oil and water. This term isdefined and explained in Principles of Colloid and Surface Chemistry,Paul C Hiemenz (2nd edition, Marcel Dekker 1986) incorporated herein inits entirety.

Suitable non-polar oils include thick mineral oils e.g. paraffin oil,sweet almond oil, isohexane, sunflower seed oil, apricot kernel oil,and/or shea butter. The non-polar oil and the polar substance arepreferably miscible i.e. a mixture containing 50% of each should exhibitno phase separation. When the non-polar oil is in the form of droplets,these preferably have a diameter of from 0.01μ, preferably from 0.1 μm,to, preferably 10 μm, more preferably 1 μm, most preferably 0.5 μm.Preferably, the composition comprises from 0.2% to 20% w/w, morepreferably from 0.2% to 4%, most preferably from 0.5% to 2% w/w of thenon-polar oil.

The surfactant and oils in the oil phase are preferably chosen so thatthe Required Hydrophilic-Lipophilic Balance (RHLB) value of the totaloil phase is of the order of the Hydrophilic-Lipophilic Balance (HLB)value of the surfactant. Preferred compositions of this invention arewherein the RHLB value of the total oil phase and the HLB value of thesurfactant are substantially equal. THE HLB value is a measure of thehydrophile-lipophile balance as discussed in Encyclopedia of EmulsionTechnology, edited by Paul Becher (pages 217-220, volume 1 (1983),Marcel Dekker) incorporated herein by reference in its entirety. TheRHLB is explained in Encyclopedia of Emulsion Technology, edited by PaulBecher (pages 353-366, volume 1 (1983), Marcel Dekker) incorporatedherein by reference in its entirety.

Preferably, the RHLB value of the total oil phase and the HLB value ofthe surfactant are each independently from 9 to 12, more preferably from10 to 11, especially about 10. The polar substance preferably has anRHLB value of from 7 to 16.

In general the surfactant is anionic, cationic or non-ionic. It ispreferably non-ionic. Examples of suitable surfactants include ceteraylphosphate, cetearyl alcohol, cetearyl glucoside, cetostearyl alcoholand/or ceteareth 20. It is preferably present in an amount of from 2.0%to 20% w/w, more preferably from 2.0% to 10% w/w, most preferably from3% to 8% w/w.

The polar substance preferably has a polarity index of from 2 to 15mN/m, more preferably from 2 to 8 mN/m. The polar substance preferablyis a polypropylene oxide-15 sterayl ether, such as that known under thetrade designation Arlamol E of ICI Ltd., having a polarity index ofabout 5.2 mN/m. More preferably the polar substance is a polar oil.Other suitable polar substances are olive oil, macadamia nut oil,avocado oil, calendula oil, wheat germ oil, and/or cyclomethiconeoptionally admixed with polypropylene oxide-15 stearyl ether.

Preferably, the composition comprises from 0.5 to 20.0% w/w, morepreferably from 0.5 to 2%, most preferably from 0.4 to 1% w/w of thepolar substance.

Optionally, the composition includes an accelerator that will acceleratethe keratin degradation reaction such as urea, thiourea, dimethylisosorbide (DMI), ethoxydiglycol (Transcutol) or methyl propyl diol (MPdiol). Preferably the accelerator is urea or methyl propyl diol. Thecomposition according to the invention preferably comprises from 5% to15% w/w, more preferably about 8% w/w of an accelerator.

It is particularly preferred for the composition further to comprise anpH regulator to assist in activating the depilatory agent. Preferablythe quantity and type of pH regulator is chosen to maintain the pH ofthe composition at a value greater than 5, preferably greater than 7,more preferably in the range of from 8 to 13, most preferably in therange of from 12 to 12.5, especially about 12. For example, by ensuringthat the pH is about 12.1 to 12.5, depilation can occur within about 5minutes, as desired by the user, without causing undue irritation.

The pH regulator preferably is in the aqueous phase (between the oildroplets) when present. Examples of the pH regulator include arginine(especially L-arginine), silicates (e.g. sodium or potassium silicate),lime and/or polyethyleneimine. It is particularly preferred for the pHregulator also to include lime in an amount of, for example, up to 3%w/w. It is preferred, in order to minimise irritation, for the totalcontent of the pH regulator to be present as less than 3% w/w, morepreferably 0.5 to 3% w/w.

In a particularly preferred embodiment of this invention, the depilatorycomposition includes, in combination, L-arginine, lime, urea, potassiumand/or dipotassium thioglycolate, the polar substance and the non-polaroil and aqueous phases.

The compositions of the invention may be formulated into a cream byadmixture with a conventional cream base, such as a mixture ofpolypropylene glycol ester and cetostearyl alcohol. The formulation mayalso include other ingredients that are conventionally present indepilatory formulations, such as perfumes, oils, and pigments andfillers such as a clay, for example, sodium magnesium silicate,magnesium trisilicate and titanium dioxide. The inclusion of a clay,preferably sodium magnesium silicate, more preferably in an amount offrom 0.1 to 10% w/w, most preferably from 0.1 to 1% w/w is particularlyadvantageous, since this provides sodium and magnesium ions for thebuffer system and improves the efficiency of depilation.

The depilatory compositions of the present invention may be prepared byany phase inversion temperature method known in the art for thepreparation of oil-in-water emulsions.

Preferably the process for preparing the composition according to theinvention comprises mixing the oil phase ingredients together at anelevated temperature of from 50° to 80° C., preferably from 60° C. to70° C.; adding the aqueous phase ingredients at a temperature of from70° to 80° C., preferably at about 75° C.; and thereafter adding thedepilatory agent at a temperature of from 30° to 40° C., preferably atabout 35° C.

An alternative process for preparing a composition according to theinvention comprises mixing the non-polar oil and the surfactant togetherat an elevated temperature of from 50° to 80° C., preferably from 60° C.to 70° C.; adding the aqueous phase at a temperature of from 70° to 80°C., preferably at about 75° C.; and thereafter adding the depilatoryagent and polar substance at a temperature of from 30° to 40° C.,preferably at about 35° C.

The admixture is preferably effected under conditions of agitationsufficient to aid mixing but insufficient to cause turbulence, morepreferably by mechanical means such as stirring. Most preferably theadmixture is carried out under conditions having a Reynold value of from0 to 2000 when the reaction is carried out in a pipe and of from 0 to 10when the reaction is carried out in a reactor vessel. Preferably theReynold value is as low as possible. The Reynold value is explained inAlthaus, Jakubith Chemistry and Chemical Engineering, memofix 1993 byVCH verlagsgesellschaft.

The depilatory agent is preferably not added until after the oil andaqueous phases have been mixed and gently cooled, for example, to about30° to 40° C., preferably about 35° C., to prevent degradation of thedepilatory agent (which occurs at substantially elevated temperatures).Any optional ingredients may be added thereafter; however it ispreferred for the clay to be added when the mixing is carried out at anelevated temperature.

Without wishing to be bound by any particular theory as to the manner inwhich the preferred depilatory compositions function, it is believedthat the oil phase is in the form of discrete droplets enveloped in abilayer structure comprising molecules of the polar substance sandwichedbetween molecules of the surfactant. Such bilayer structures are thenseparated from each other by the continuous aqueous phase (i.e. bilayeraqueous phase) to form a multi-bilayer structure. About 30 to 50% w/w ofthe keratin-degrading substance tends to be embedded in the surface ofthis multi-bilayer structure, with the remainder being in the aqueousphase. The embedded keratin-degrading substance is released from themulti-bilayer structure only as it is needed for depilation. Thus, whenthe keratin-degrading substance in the continuous aqueous phase has beenused up in the depilation process, the keratin-degrading substanceembedded in the multi-bilayer structure is thermodynamically driven outby entropy and can then diffuse into the hair shaft to effectdepilation. In this way, the depilatory composition acts as a reservoirof keratin-degrading substance whose release is regulated during use.Thus the composition according to the invention has the advantage of alower irritancy. This reduced irritancy is further improved by theabsence of tertiary amines from the composition.

According to the invention there is further provided the use of acomposition according to the invention to degrade hair keratin.

Throughout this specification, “w/w” refers to the weight of the totalcomposition, unless otherwise specified.

The following Examples illustrate the invention.

EXAMPLE 1

A depilatory composition was prepared from the following ingredients:

Ingredient w/w total composition Cetostearyl alcohol (2) 8.0% Sodiummagnesium silicate 1% Ca (OH)₂ (3) 0.5% Urea (3) 8.0% L-arginine (3)2.0% Polyethylenimine (3) 1.0% Magnesium trisilicate 0.5% Titaniumdioxide (3) 0.33% Potassium thioglycolate (30%) 10.0% Shea Butter (1)0.5% Perfume 0.5% Paraffin oil (1) 3.5% Propylene glycol (3) 0.26%Acrysol 33 0.01% Arlamol E (4) 1.0% Ceteareth 20 (2) 3.0% Deionisedwater to 100% *Acrysol 33 is an acrylic copolymer available from Rohm &Haas.

The method is as follows: the non-polar oils (I) were heated to 60° C.,the surfactants (2) added and the mixture stirred in a reactor vesselhaving a Reynold value of less than 10. Whilst continuing to stir, thetemperature was raised to about 75° C. In the meantime, the aqueousphase ingredients (3) were added with about 50% of the water. Theaqueous phase as then added, at 75° C., to the oil phase with gentlestirring, and the mixture allowed to cool slowly to 35° C. At thistemperature, the active ingredient (4) was added with gentle stirringand then the remaining ingredients.

The resultant cream had a pH of 12.3 and was in the form of discretedroplets formed of the shea butter, at least some of the perfume oil andthe paraffin oil, separated by a bilayer structure formed of thecetostearyl alcohol, Ceteareth 20, potassium thioglycolate, some of thepropylene glycol and the Arlamol E from a continuous aqueous phasecontaining the remainder of the ingredients. It satisfactorily removedunwanted hair within about 5 minutes, without causing undue irritationto the skin.

EXAMPLE 2

A depilatory composition was prepared according to the method used inExample 1 from the following ingredients:

Ingredient w/w total composition Cetostearyl alcohol (2) 8.0% Sodiummagnesium silicate (3) 1% Ca (OH)₂ (3) 0.5% Urea (3) 8.0% L-arginine (3)2.0% Polyethylenimine (3) 1.0% Magnesium trisilicate (3) 0.5% Titaniumdioxide (3) 0.33% Potassium thioglycolate (30%) 10.0% Shea Butter (1)0.5% Perfume (4) 0.5% Paraffin oil (1) 3.5% Propylene glycol (3) 0.26%Acrysol 33 0.01% Arlamol E (4) 1.0% Ceteareth 20 (2) 3.0% Deionisedwater to 100% *Acrysol 33 is an acrylic copolymer available from Rohm &Haas.

The composition satisfactorily removed unwanted hair within about 5minutes, without causing undue irritation to the skin.

EXAMPLE 3

A depilatory composition was prepared according to the method used inExample 1 from the following ingredients:

Ingredient w/w total composition Cetostearyl alcohol (2) 8.0% Sodiummagnesium silicate (3) 1% Ca (OH)₂ (3) 0.5% Urea (3) 8.0% L-arginine (3)2.0% Polyethylenimine (3) 1.0% Magnesium trisilicate (3) 0.5% Titaniumdioxide (3) 0.33% Potassium thioglycolate (30%) 10.0% Shea Butter (1)0.5% Perfume (4) 0.5% Paraffin oil (1) 3.5% Propylene glycol (3) 0.26%Acrysol 33 0.01% Arlamol E (4) 1.0% Ceteareth 20 (2) 3.0% Deionisedwater to 100% *Acrysol 33 is an acrylic copolymer available from Rohm &Haas.

The composition satisfactorily removed unwanted hair within about 5minutes, without causing undue irritation to the skin.

EXAMPLE 4

A depilatory composition was prepared according to the method used inExample 1 from the following ingredients:

Ingredient w/w total composition Cetostearyl alcohol (2) 8.0% Sodiummagnesium silicate (3) 1% Ca (OH)₂ (3) 0.5% Urea (3) 8.0% L-arginine (3)2.0% Polyethylenimine (3) 1.0% Magnesium trisilicate (3) 0.5% Titaniumdioxide (3) 0.33% Potassium thioglycolate (30%) 10.0% Shea Butter (1)0.5% Perfume (4) 0.5% Paraffin oil (1) 3.5% Propylene glycol (3) 0.26%Acrysol 33 0.01% Arlamol E (4) 1.0% Montanov 68** (2) 5.0% Deionisedwater to 100% *Acrysol 33 is an acrylic copolymer available from Rohm &Haas. **Montanov 68 is a mixture of cetearyl alcohol and cetearylglucoside available from Seppic.

The composition satisfactorily removed unwanted hair within about 5minutes, without causing undue irritation to the skin.

What is claimed is:
 1. A depilatory composition in the form of anoil-in-water emulsion which comprises: from 2% to 6% w/w of a depilatoryagent; from 4.7% to 66% w/w of an oil phase comprising, as a percentageof the depilatory composition, from 0.2% to 20% w/w of a non-polar oilin the form of droplets having a diameter of from 0.01 to 10 μm and apolarity index of from 20 to 40 mN/m, from 2% to 20% w/w of a surfactanthaving a HLB value of from 9 to 12, and from 0.5% to 20% of a polarsubstance having a polarity index of from 2 to 15 mN/m, the oil phasehaving a RHLB value of from 9 to 12; and from 5.3% to 34% of an aqueousphase comprising L-arginine and lime as pH regulators, wherein thedepilatory agent is present in both the oil phase and the aqueous phaseand the depilatory composition is substantially free from tertiaryamines.
 2. A composition according to claim 1 wherein the depilatoryagent is selected from the group consisting of potassium thioglycoate,dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicyclicacid, N-acetyl-L-cysteine, lipoic acid, NaHSO₃, Li₂S, Na₂S, K₂S, MgS,CaS, SrS, BaS, (NH₄)₂S, sodium dihydrolipoate, sodium6,8-dithiooctanoate, NaSH, KSH, thioglycolic acid, thioglycerol,2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid,ammonium thioglycolate, glyceryl monothioglycolate, monoethanolaminethioglycolate, monoethanolamine thioglycolic acid, diammoniumdithiodiglycolate, ammonium thiolactate, monoethanolamine thiolactate,thioglycolamide, homocysteine, cysteine, glutathione, dithiothreitol,dihydrolipoic acid, 1,3-dithiopropanol, thioglycolamide,glycerylmonothioglycolate, thioglycolhydrazide, keratinase, hydrazinesulphate, hydrazine disulphate, triisocyanate, guanidine thiglycolate,calcium thioglycolate and cysteamine.
 3. A composition according toclaim 2 wherein the depilatory agent is potassium thioglycolate.
 4. Acomposition according to claim 1 wherein the RHLB of the total oil phaseand the HLB of the surfactant are substantially equal.
 5. A compositionaccording to claim 1 wherein the non-polar oil is selected from thegroup consisting of thick mineral oil, sweet almond oil, isohexane,sunflower seed oil, apricot kernel oil, shea butter, and mixturesthereof.
 6. A composition according to claim 1 wherein the surfactant isselected from the group consisting of cetearyl phosphate, cetearylalcohol, cetearyl glucoside, cetostearyl alcohol, Ceteareth 20, andmixtures thereof.
 7. A composition according to claim 1 wherein thepolar substance is selected from the group consisting of polypropyleneoxide-15 stearyl ether, olive oil, macadamia nut oil, avocado oil,calendula oil, wheat germ oil, cyclomethicone, and mixtures thereof. 8.A composition according to claim 1 which additionally comprises anaccelerator that will accelerate the action of the depilatory agent indegrading keratin.
 9. A composition according to claim 8 wherein theaccelerator is selected from the group consisting of urea, thiourea,dimethyl isosorbide, ethoxydiglycol, methylpropyldiol, and mixturesthereof.
 10. A composition according to claim 9 in which the acceleratoris urea and is present in the aqueous phase.
 11. A composition accordingto claim 1 further comprising a clay in an amount of from 0.1% to 10%w/w.
 12. A composition according to claim 1 which is in the form of acream.
 13. A process for preparing a composition as defined in claim 1which process comprises the steps of: mixing the oil phase ingredientstogether at a temperature of from 50° to 80° C.; adding the aqueousphase ingredients at a temperature of from 70° C. to 80° C.; andthereafter adding the depilatory agent at a temperature of from 30° to40° C.
 14. A processing for preparing a composition as defined in claim1 which process comprises the steps of: mixing the non-polar oil and thesurfactant together at a temperature of from 50° to 80° C.; adding theaqueous phase at a temperature of from 70° to 80° C.; and thereafteradding the depilatory agent and polar substance at a temperature of from30° to 40° C.
 15. A process according to claim 14, wherein the mixingand addition steps are effected under conditions of agitation sufficientto aid mixing but insufficient to cause turbulence.
 16. A method forremoving unwanted hair which comprises the steps of: (1) applying to anarea of the body from which depilation is desired a depilatorycomposition in the form of an oil-in-water emulsion which comprises:from 2% to 6% w/w of a depilatory agent; from 4.7% to 66% w/w of an oilphase comprising, as a percentage of the depilatory composition, from0.2% to 20% w/w of a non-polar oil in the form of droplets having adiameter of from 0.01 to 10 μm and a polarity index of from 20 to 40mN/m, from 2% to 20% w/w of a surfactant having a HLB value of from 9 to12, and from 0.5% to 20% of a polar substance having a polarity index offrom 2 to 15 mN/m, the oil phase having a RHLB value of from 9 to 12;and from 5.3% to 34% of an aqueous phase comprising L-arginine and limeas pH regulators, wherein the depilatory agent is present in both theoil phase and the aqueous phase and the depilatory composition issubstantially free from tertiary amines; (2) allowing said compositionto remain on the skin for sufficient time to degrade keratin present insaid hair; and (3) removing said composition together with the unwantedhair.
 17. A method according to claim 16 in which, in the composition,the depilatory agent is potassium thioglycolate, and urea isadditionally present as an accelerator.